When color space of image data is converted to the CMYK color space, gray may be reproduced by mixture of four coloring materials, that is, cyan (C), magenta (M), yellow (Y) and black (K) coloring materials, or by only black (K) coloring material is used. When the gray is reproduced by the mixture of four coloring materials, good tone continuousness can be provided between gray areas and chromatic color areas therearound. When it is reproduced by the black coloring material, the gray areas look sharp.
In a known system, reproducing gray either by mixture of CMYK or by black is determined depending on whether a chromatic color area is present around the gray area.
In the known system, a chromatic area is present around a gray area, reproducing gray by the mixture of CMYK. And In the known system, reproducing gray reproduces by black when a chromatic color area is not present around the gray area.
however in the known system, the gray is not always reproduced appropriately for objects. This is because the best way to reproduce gray depends on an attribute of an object that includes the gray pixels. Therefore, there is a need in the art to reproduce gray appropriately for different types of objects in an image processing device and an image forming apparatus, and an image processing program that can enable the reproduction of gray suitable for different types of objects is needed.